## 洛谷 P3381 【模板】最小费用最大流

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6+10;
const int inf = 0x3f3f3f3f;
struct node{
int v, w, nxt, f;
}edge[N];
int n, m, st, ed, cnt, mc, mf;
int fir[N], dis[N], fl[N], fa[N];
//dis[N] 费用的最短距离
//fl[N]  最短路径上的最小流量
//fa[N]  记录最短路径
bool vis[N];
inline void add(int u, int v, int w, int f){
edge[++cnt] = (node){v, w, fir[u], f}; fir[u] = cnt;
edge[++cnt] = (node){u, 0, fir[v], -f}; fir[v] = cnt;
}
inline int spfa(){
memset(vis, false, sizeof(vis));
vis[st] = true;
memset(dis, 0x3f3f3f3f, sizeof(dis));
dis[st] = 0;
queue<int> q;
q.push(st);
fl[st] = inf;
while(!q.empty()){
int u = q.front();
q.pop();
vis[u] = false;
for(int i = fir[u]; i; i = edge[i].nxt){
int v = edge[i].v;
if(edge[i].w && dis[v] > dis[u] + edge[i].f){
dis[v] = dis[u] + edge[i].f;
fl[v] = min(fl[u], edge[i].w);
fa[v] = i;
if(!vis[v]){
vis[v] = true;
q.push(v);
}
}
}
}
return dis[ed] != inf;
}
inline void MCMF(){
while(spfa()){
int x = ed;
mf += fl[ed];
mc += fl[ed] * dis[ed];
while(x != st){
int i = fa[x];
edge[i].w -= fl[ed];
edge[i^1].w += fl[ed];
x = edge[i^1].v;
}
}
}
int main(){
#ifdef ONLINE_JUDGE
#else
freopen("in.txt", "r", stdin);
#endif //ONLINE_JUDGE
int a, b, c, d;
cnt = 1;
mc = 0, mf = 0;
memset(fir, 0, sizeof(fir));
scanf("%d%d%d%d", &n, &m, &st, &ed);
for(int i = 1; i <= m; i++){
scanf("%d%d%d%d", &a, &b, &c, &d);